WO2025136937A1

WO2025136937A1 - Devices and methods for aligning prosthetic and orthotic components

Info

Publication number: WO2025136937A1
Application number: PCT/US2024/060498
Authority: WO
Inventors: Bjoern ALTENBURG; Douglas Rush
Original assignee: Otto Bock Healthcare LP
Current assignee: Otto Bock Healthcare LP
Priority date: 2023-12-20
Filing date: 2024-12-17
Publication date: 2025-06-26
Anticipated expiration: 2026-06-20

Abstract

A joint of a prosthetic or orthotic device is provided with reference features which visually convey whether or not the joint is in a target position such as neutral position. A first reference feature and the second reference feature have a spatial relation that changes based on the angle between links of the joint. An alignment of the first and second reference features indicates the joint is in the neutral position. Conversely, a non-alignment of the first and second reference features indicates the joint is not in the neutral position.

Description

DEVICES AND METHODS FOR ALIGNING PROSTHETIC AND ORTHOTIC COMPONENTS

FIELD OF THE INVENTION

The present disclosure relates generally to prosthetic and orthotic devices, and, more particularly, joints for devices such as but not limited to prosthetic ankle/feet. This disclosure is directed to prosthetic joints and components for use external to the human body, meaning the devices disclosed are not intended for implantation into the human body.

BACKGROUND

Lower limb prosthetic components must be aligned by a prosthetist to achieve their intended optimal function. In the case of an ankle/foot, the objective is to replicate a sound human ankle/foot as closely as possible.

Industry standard prosthetic connection components or adapters allow angular adjustment in both the coronal plane (with rotation about an axis oriented in the anterior-posterior direction) and the sagittal planes (with rotation about an axis oriented in the medial-lateral direction). Connection components which allow planar movement in the transverse plane also exist but are typically heavier and more expensive. For example, a simple prosthetic leg is typically comprised of a prosthetic foot, a prosthetic socket, and a pylon which connects the foot to the socket and establishes the correct leg length. Each of these components typically has a prosthetic pyramid adapter located on the distal end, on the proximal end, or on both ends. Accurate alignment of adjustable components is necessary to achieve the desired response of the prosthesis, which means a prosthetic component must have the correct orientation in space relative to both the human body and other prosthetic components.

Prosthetic components with an axis of motion present unique alignment challenges because the moveable component can be oriented anywhere within the range of motion. This introduces another variable to getting the “right” alignment for an amputee. Prosthetic legs, for example, typically undergo two stages of alignment. The first is “bench alignment” where the prosthetist assembles the leg using an assembly fixture to meet the requirements of the amputee. Bench alignment is typically performed to replicate a standing position. Further adjustments are made during a final alignment stage, which occurs with the patient using the prosthesis. The final alignment stage is commonly referred to as dynamic alignment. Dynamic alignment occurs with an amputee using the prosthetic limb under the supervision of a prosthetist. During dynamic alignment a prosthetist makes length and/or angular adjustments to the components of a limb based on training, experience, and feedback from the amputee to optimize the amputee’s gait. If the limb includes components with additional adjustable features such as adjustable stiffness, hydraulic resistance and/or the timing of resistance, these features may also be adjusted. If the prosthetist fails to achieve the goal of near optimal alignment during bench alignment it will not be known until the final alignment stage, and significant effort may be required to correct the issue, such as completely refabricating a socket or at least requiring additional alignment components. This results in increased cost and weight of the prosthetic limb and a delay in the amputee receiving the functional limb.

SUMMARY

According to one aspect of some exemplary embodiments, one or more visual reference features are provided on a prosthetic component (or components) with at least one axis of pivoting motion. Reference or alignment features such as alignment marks or three-dimensional contours or edges used for alignment allow a prosthetist to orient the joint in the correct position within the range of motion during an alignment procedure. Reference or alignment features facilitate the construction and alignment process of a prosthetic joint which utilizes a component with a range of motion. Exemplary embodiments relate variously to joints, which may include but are not limited to prosthetic or orthotic ankles, feet, knees, hips, elbows, shoulders, and wrists.

According to one aspect of some exemplary embodiments, reference or alignment features are provided on a prosthetic component of an ankle -foot prothesis with an axis of motion. The reference or alignment features allow a prosthetist to orient the ankle/foot or knee in the correct position within the range of motion during both bench alignment and final alignment. Reference or alignment features facilitate the construction and alignment process of a prosthetic limb which utilizes a component with a range of motion. Common prosthetic components which have a pivoting axis of motion may have a limited range of motion. The components may also have a biased range of motion in which one or more springs biases the orientation of a first component relative to a second component to a position located at one end of the range of motion. Alternatively, the first component may be biased to a position within the range of motion but not at the end of the range. Some pivoting prosthetic components do not pivot around a stationary axis of rotation because they may be connected by a linkage which results in a moving axis of rotation, which is also known as an instantaneous center of rotation. Such prosthetic components are frequently described as polycentric.

While the employment of at least two reference features in combination with one another is especially useful for visually conveying when a prosthetic joint is at the neutral position, those of ordinary skill in the art will appreciate that reference features according to this disclosure may be employed to convey other positions of the prosthetic joint. In particular, any position (e.g., specific rotational/angular position or specific longitudinal position) which cannot be readily and reliably determined by visual inspection alone, absent the presence of at least two reference features (which may also be referred to as alignment features) the combination of which is provided expressly for this purpose, may be advantageously conveyed by the employment of such reference features according to this disclosure. Generally, this is most desirable for any position of the prosthetic which is needed when the prosthetic joint is being set up, aligned (as by a prosthetist), calibrated, and/or tuned.

In some embodiments, a joint assembly with a range of pivoting motion is forced to assume and maintain a single target position within the range using a temporarily positioned or attached further link. This temporary alignment link may be a strut, for example. In an exemplary ankle assembly, the strut may be attached or positioned at the back of the ankle. The strut is positioned or attached between two rotating parts, and it sets an angular position so long as it remains in its seated position or attached position.

Following is an example method for the alignment of a prosthetic joint that comprises a joint assembly with a range of pivoting motion, the joint assembly comprising a first link rotatably connected to a second link such that an angle between the first link and the second link is changeable between a minimum angle and a maximum angle, wherein the joint is configured to have a neutral position corresponding to a single angle measure between the minimum angle and the maximum angle. The method may include placing the joint assembly in the neutral position by aligning a first reference feature on the first link with a second reference feature on the second link, wherein the first reference feature and the second reference feature have a spatial relation that changes based on the angle between the first and second links, wherein an alignment of the first and second reference features indicates the joint is in the neutral position, and a non- alignment of the first and second reference features indicates the joint is not in the neutral position. Alternatively, the joint assembly may be placed in the neutral position by temporarily attaching or positioning an alignment link with a fixed length within the ankle assembly such that the joint assembly is fixed at the neutral position within the range of pivoting motion. After the joint assembly is aligned in the single target position by whichever of these alignment techniques, the method may include the further steps of: performing one or more alignment procedures to the ankle-foot prosthesis while the alignment link is in the ankle assembly or the first and second reference features are aligned; and permitting the ankle assembly to move through the range of pivoting motion by removing the alignment link or permitting non- alignment of the first and second reference features.

Exemplary embodiments may include, for example, one or more mechatronic components configured to confirm when a prosthetic or orthotic joint is in a neutral position. The confirmation may be given as an audible beep or a visual confirmation via an app on a device which is physically separate and apart from the prosthetic or orthotic. Some exemplary embodiments may give confirmation/indication of a neutral position/calibration with an indicator light source, e.g., one or more LEDs, which may be configured to change (e.g., illuminate, change color, change illumination pattern such as from solid to flashing, etc.) to indicate neutral position or calibration. Some exemplary embodiments may give confirmation/indication of a neutral position/calibration via an included joint angle encoder, for example an encoder based on the Hall Effect, which measures the strength of a magnetic field and hence the distance of a sensor from a magnet.

Some exemplary embodiments may specifically exclude any electronic and/or magnetic components (such as those listed in the preceding paragraph) for the purpose of indicating or confirming when a joint assembly is in a neutral position. That is to say, some embodiments may be devoid or free of any mechatronic components, audio components, illumination components, software components, digital components, processors (including microprocessors), external device app connectivity, joint angle encoders, and/or Hall effector sensors for the purpose of indicating a neutral position. It will be appreciated that such types of elements may or may not be included in a prosthetic or orthotic for purposes separate and apart from indicating a neutral position or other angular positions. A significant aspect of many embodiments, irrespective of whether or not certain electrical and/or magnetic components are included, is a clear and simple visual indicator which reliably and intuitively conveys by unaided visual inspection whether or not a joint assembly is in a position of significance, in particular the neutral position. Neutral position may be ascertained exclusively by visual inspection of the physical prosthetic or orthotic without accessories such as computer/mobile applications or even electrical power. Neutral rotational position (or an alternative target position) of a joint may not be visually ascertainable (e.g., within a predetermined range of accuracy and precision) except by the reference features expressly provided for this purpose. The degree of certainty required may be a tolerance of 0.1 degree from the true angle, or 0.25 degrees, or 0.5 degree, or 0.75 degree, or 1 degree, or 1.25 degree, or 1.5 degrees, or 1.75 degrees, or 2 degrees, or some other tolerance value.

In some embodiments, a variable extent to which a joint is not in the neutral position may be visually conveyed. Some users may benefit from a device which conveys by simple visuals whether the device is comparatively near or far from being in the neutral position. In some situations this configuration can be advantageous over alternative devices which may convey only a binary status, such as whether the device is or isn’t in the neutral position without any further information on the degree or extent to which the device is not in the neutral position. Some exemplary embodiments may be configured to provide such further information of the degree or extent to which the device is not in a target position such as neutral position. First and second references features which are both simultaneously visible on an exterior of a prosthesis or orthotic may be configured such that a physical space/gap/distance between the first and second reference features visibly increases (e.g., in a continuous or smooth transition) in size when (e.g., whenever) the joint is changing position (I) away from the neutral position and (ii) toward the maximum angle and/or minimum angle of joint rotation. Relatedly, the first and second references features may also (or instead) be configured such that the physical space/gap/distance between the first and second reference features visibly decreases (e.g., in a continuous or smooth transition) in size when (e.g., whenever) the joint is changing position (a) toward the neutral position and (ii) away from the maximum angle and/or minimum angle of joint rotation. The first and second reference features may both be simultaneously visible on an exterior of the ankle-foot prosthesis for at least some angles within the range of angles. In some embodiments, at least one of the first and second reference features may be obstructed from external view at certain angles, e.g., all rotational positions in between the neutral rotational position and the limit to rotation in the flexion direction, or else all rotation positions in between the neutral rotational position and the limit to rotation in the extension direction.

For the purposes of this disclosure, flexion of an ankle joint has the same meaning as dorsiflexion, and extension of the ankle joint has the same meaning as plantarflexion. Flexion of a wrist joint rotates the ventral surface of the hand (the palm) hand toward the ventral surface of the forearm, and extension rotates the dorsal surface of the hand (the back of the hand) towards the dorsal surface of the forearm. Extension of a knee or elbow joint straightens the leg or arm and flexion bends the knee or elbow.

In a joint with multiple links, each link may be extendable/retractable to any of a plurality of different lengths or else restricted to a single permanent length. Generally, any pair of links which are directly linked to one another may be configured to have exemplary reference features the alignment of which conveys the joint is in particular target position. The largest angle two connected links are permitted to make may correspond with maximum flexion or else maximum extension of the joint. The smallest angle two connected links are permitted to make may correspond with maximum extension or maximum flexion. Given three links connected to form a force triangle within a prosthetic joint, for example, there are three angles in the triangle. As the joint flexes, at least one angle in the force triangle increases in size while at least one other angle simultaneously decreases in size. As the joint extends, at least one angle in the force triangle decreases in size while at least one other angle simultaneously increases in size. Accordingly, whether a particular minimum angle value between a pair of links corresponds with a maximum or minimum angle of the overall joint depends on which pair of links are the subject of discussion. Similarly, whether a particular maximum angle value between a pair of links corresponds with a maximum or minimum angle of the overall joint depends on which pair of links are the subject of discussion. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 A is schematic of a prosthetic or orthotic joint with at least two links.

Figure IB is a schematic of a prosthetic or orthotic joint with at least three links arranged together to form a force triangle.

Figure 2A is a schematic of a joint in which two connected links are at a maximal rotational distance from one another.

Figure 2B is a schematic of the joint of Figure 2A when the two connected links are at a neutral position with respect to one another.

Figure 2C is a schematic of the joint of Figure 2A in which the two connected links are at a minimum rotational distance from one another.

Figure 3A is a representation of a typical gait cycle of a healthy non-amputee human adult walking without the assistance of any protheses or orthoses.

Figure 3B is a graph of typical ankle moments during a normal gait cycle.

Figure 4 is an exemplary prosthetic foot system including a footshell and prosthetic foot.

Figures 5A, 5B, and 5C are alternative perspective views of an exemplary prosthetic foot.

Figure 5D is an exploded view of the exemplary prosthetic foot of Figures 5A-5C.

Figure 6A is another exploded view showing various alignment features of the exemplary prosthetic foot.

Figure 6B is a perspective view of the exemplary prosthetic foot including ankle assembly with alignment features appearing on the left side of the device.

Figure 7A is an exemplary prosthetic foot in a maximal dorsiflexion position.

Figure 7B is the prosthetic foot in the neutral position.

Figure 7C is the prosthetic foot in a maximal plantarflexion position.

Figure 8A is a prosthetic ankle assembly set to a target position by a temporary alignment link which is attached to the assembly.

Figure 8B is a prosthetic ankle assembly set to a target position by a temporary alignment link which is positioned within the assembly.

Figure 9 is an exemplary prosthetic leg.

Figure 10 is an exemplary prosthetic foot system in a neutral stance. Figure 11 is the prosthetic foot system at maximum plantarflexion such that the pyramid angle of the pyramid connector is zero degrees.

Figure 12 is the prosthetic foot system positioned with the pyramid angle of the pyramid connector at two degrees.

Figure 13 is the prosthetic foot system at maximum dorsiflexion such that the pyramid angle of the pyramid connector is zero degrees.

DETAILED DESCRIPTION

Figure 1 A is a schematic of a prosthetic or orthotic joint 10. For purposes of this disclosure, an assembly or component may be qualified as “prosthetic”, but it will be understood that exemplary embodiments may likewise be applied to “orthotic” equivalents. The joint 10 includes a first part, in particular a first link 11, and a second part, in particular a second link 12. The first link 11 and second link 12 are rotatably connected with one another at a pivot point 13. The joint 10 may belong to any prosthesis or orthosis for which a range of rotational motion is desired. An exemplary prosthesis with a joint 10 may be a substitute for a biological ankle, foot, knee, hip, elbow, shoulder, or wrist, for example. An exemplary orthosis may support or alleviate the load to one or more of these joints.

Irrespective of the biological joint for which the prosthesis substitutes, the joint 10 permits rotation in both flexion and extension directions. As with biological joints, it may be desirable that a prosthetic or orthotic joint 10 have limits to both flexion and extension, or alternatively flexion and extension limits may be the result of practical cost, weight, or other mechanical design limitations or decisions. To this end, joint 10 includes a first stop 15 and a second stop 16. In Figure 1A the stops 15 and 16 are illustrated schematically and may, in different embodiments, take any of a variety of different forms. The first stop 15 is configured to establish a limit to rotation which establishes the minimum angle 0mi_u which may exist between links 11 and 12. The second stop 16 is configured to establish a limit to rotation which establishes the maximum angle 0_max which may exist between links 11 and 12. Generally, the joint 10 may be configured to permit the angle between links 11 and 12 to be any angle value from 0min to 0_max. For the sake of illustration, Figure 1 adopts a frame of reference in which first link 11 appears to stay in one position while second link 12 rotates with respect to first link 11. Accordingly, dotted line 17 shows the rotational position of second link 12 at which the second link 12 cannot move any nearer to link 11. When the second link 12 is at position 17, the angle between links 11 and 12 is angle 0_min. Dotted line 18 shows the rotational position of second link 12 at which the second link 12 cannot move any further from link 11. When the second link 12 is at position 18, the angle between links 11 and 12 is angle 0_max.

In the Earth’s frame of reference, flexion and extension of joint 10 may each involve only the second link changing position, or only the first link changing position, or indeed both the first link and second link changing positions concurrently. Irrespective of the frame of reference, the angle between links 11 and 12 is confined to be from Omin to 0_max. With respect to first link 11, the second link 12 rotatable to and from any rotational position between the stops 15 and 16 during use of the prosthesis or orthotic.

Dotted line 14 shows a rotational position of particular significance, namely the neutral position 14 which is the angle between links 11 and 12 when the joint 10 is in its neutral position. The neutral rotational position is angle 0_n. The neutral position of a prosthesis, depending on the biological joint being substituted and the particular context of use, may equal 0min or 0_max. However, of particular interest in this disclosure are protheses and orthoses for which the neutral position is between the flexion and extension limits, that is to say 0_min < 0n < 0max. It is within this context that the particular problems outlined in the Background above is especially acute, namely the difficulties of accurately knowing the neutral position during alignment of a prosthesis for use by a particular wearer.

In the context of prosthetic devices, the term “neutral position” may refer to a specific resting or default position of the artificial joint. The neutral position may be the position in which the prosthetic limb is not actively performing any specific movement or exerting force. The neutral position is often designed to mimic the resting anatomical position or a natural resting position of the corresponding biological joint and related limb. For example, in the case of a prosthetic arm, the neutral positions of the pertinent joints (which may include one or more of shoulder, elbow, and wrist, depending on the extent of the biological arm being substituted) are such that the prosthetic arm is positioned alongside the body, with the elbow slightly bent and the hand in a relaxed position. This position is typically chosen to provide a comfortable and natural appearance when the prosthesis is not actively being used for specific tasks or actions. The neutral position is important for several reasons. It allows the prosthesis to blend in visually with the user’s body, making the prosthesis appear more natural and less conspicuous. Additionally, a neutral position may serve as a starting point or reference for the user to initiate specific movements or gestures with the prosthesis. By returning to the neutral position after performing a task, the user can easily reset the position of the prosthesis. In some prostheses, mechanical systems may be configured to automatically return a prosthetic joint to the neutral position when the joint is not in use for performing any tasks. In the context of ankle/feet prostheses, the neutral position is sometimes the standing position, which is to say the neutral position is an angle Ou desirable when the user is standing still with some of the user’s weight (e.g., approximately half of the user’s weight) placed upon the ankle/foot prosthesis. The exact value of the neutral position angle 0_n depends in part on the particular configuration of prosthetic components. In general, there is typically a single angular position of a joint that constitutes the neutral position for that joint. Accordingly there is also only a single neutral position for many cases (but not necessarily all cases). For a human ankle the neutral or standing position results in a tibia angle of 4 degrees from a vertical position, wherein the proximal end of the tibia is located anterior to the distal end (I.e., the tibia is leaning forward). The alignment orientations of prosthetic components may be somewhat different than intact human anatomy due to mechanical design trade-offs and historical context. Significant deviations from historical norms can result in customer confusion and complaints.

For simplicity of illustration, Figure 1A depicts joint 10 as having only a first link 11 and second link 12. For a variety of applications, the prosthetic joint 10 may include one or more further links, especially at least a third link. Depending on the application, links of a joint 10 may be of fixed lengths, variable lengths, or some combination of fixed and variable length links.

Figure IB shows a joint 10' which is substantially the same as joint 10 of Figure 1A, but for the addition of a third link 19 which connects links 11 and 12 with one another. Third link 19 and first link 11 are rotatably connected with one another at pivot point 21. Third link 19 and second link 11 are rotatably connected with one another at pivot point 22.

One or more of the links 11, 12, and 19 may be an extendable link. An extendable link may also be referred to interchangeably as a retractable link, or simply a variable length link. An advantageous configuration for some applications is that first and second links 11 and 12 are of fixed lengths, and the third link which connects to both the first and second links 11 and 12 is extendable. By the extension and retraction of the third/extendable link 19, the third link 19 influences (or may even be configured to fully control in some applications) any changes of the angle between first and second links 11 and 12 within the range 0_niin to 0_max. The stops 15 and 16 may be incorporated within the third link 19. For instance, the stop 15 may establish the minimum length to which the extendable link may retract, and the stop 16 may establish the maximum length to which the extendable link may extend. An extendable link may include or consist of, for example, a hydraulic cylinder or a linear actuator. The travels limits of the piston within a hydraulic cylinder may constitute the stops 15 and 16. The travel limits may be defined by the ends of the chamber housing the piston.

According to some configurations, the first stop 15 may be configured to establish a limit to rotation in the flexion direction, while the second stop 16 is configured to establish a limit to rotation in the extension direction. Within this context, dotted line 17 shows the position of maximum flexion for second link 12. When the second link 12 is at position 17, the angle 0min between links 11 and 12 is the maximum flexion angle. When the second link 12 is at position 18, the angle 0_max between links 11 and 12 is the maximum extension angle. However, in some embodiments these descriptors may be reversed. Depending on the overall configuration of the prosthesis, the angle 0_min may correspond with the prosthetic joint being at maximum extension, and the angle 0_max may correspond with the prosthetic joint being at maximum flexion. Further examples below will provide greater illustration of this point.

When speaking of angles, those of ordinary skill in the ail will appreciate that some prosthetics and orthotics may have a variety of part pairings with each pair forming its own angle. The arrangement of links in joint 10' in Figure IB conveys how at any given static moment in time, links 11 and 12 form a first angle, links 12 and 19 form a second angle, and links 11 and 19 form a third angle. When the length of extendable link 19 changes, the numerical values of all three angles — the first angle, second angle, and third angle — may change. One of these angles may or may not also be the angle of the overall joint and/or the overall prosthesis. Generally speaking, however, when a joint is in a neutral position, the respective angles formed by components which are moveable relative to one another are also in respective neutral positions. However, the numerical angle of a joint (expressed in degrees or radians) when the joint is in a neutral position may or may not equal the numerical angle (expressed in degrees or radians) of any pair of links belonging to the joint. Generally, for exemplary embodiments of this disclosure, when two links are described as having a neutral angle/position between themselves, it may be inferred that other link pairings are simultaneously in their neutral angle/position, and the overall joint is in its neutral position. Conversely, when a joint is in a neutral position, respective pairs of components within the joint are simultaneously at rotational positions relative to one another which are described as their neutral positions. A joint’s ankle is often measured from pure vertical or else from horizontal (a flat surface), unless context indicates otherwise. A link’s angular position may be given from pure vertical or horizontal, or else relative to another link. The latter scenario was employed above to describe the figures thus far.

Exemplary embodiments address the problem of easily recognizing, with accuracy and repeatability, when a prosthetic joint like joints 10 and 10' is in its neutral position and when it is not. This is achieved by, for example, one or more particular reference features (e.g., visual markers) provided specifically for this purpose.

Figures 2A, 2B, and 2C depict the joint 10 or 10' with the links 11 and 12 at the maximum angle 0_max, at the neutral position 0_n, and at the minimum angle 0_min, respectively. Features such as a third link and stops are omitted from illustration for better clarity of certain other features. The first link 11 has a first reference feature 24, and the second link 12 has a second reference feature 25. As is apparent from a comparison of Figures 2 A, 2B, and 2C with one another, the first reference feature 24 and the second reference 25 feature have a spatial relation that changes based on the angle between the first and second links. In the neutral position of the joint, depicted by Figure 2B, the reference features 24 and 25 align with one another. For purposes of this schematic, alignment involves the black dot (or the corner of the physical component A on which it appears) coinciding with the white circle (or the comer of the physical component B on which it appears). As apparent from Figures 2A and 2C, alignment of the references features 24 and 25 does not exist at either the maximum or minimum angles of the joint. Nor does it exist at any other angle between links 11 and 12 except for the neutral position. Accordingly, an alignment of the first and second reference features 24 and 25 conveniently and unequivocally indicates the joint 10/10' is in the neutral position. Correspondingly, a non- alignment of the first and second reference features 24 and 25 indicates the joint 10/10' is not in the neutral position.

In the case of joints with three or more links, e.g. joint 10' of Figure IB, which result in multiple internal angles to the joint, reference features may be applied to any combination of the links. In Figure 2B, the two links should be understood as representative of any pair of links which are rotatably connected with one another. Accordingly, reference features like features 24 and 25 may be applied respectively to links 11 and 12 of joint 10' of Figure IB, or to links 11 and 19 of joint 10' of Figure IB, or to links 12 and 19 of joint 10' of Figure IB. One, two, or all three of these pairings may each have its own set of reference features, depending on the embodiment.

Exemplary reference features may take a variety of forms, including but not limited to indicia (e.g., the black dot and white circle in Figures 2A-2C) and/or physical contours of solid three-dimensional structures (e.g., the physical comers of physical components A and B which meet and overlap in Figure 2B). The schematics of Figures 2A-2C are intended to broadly illustrate any of these options. Further exemplary embodiments which elaborate on available alternatives are described below.

For purposes of exemplary illustration, an ankle/foot prosthesis will be described next with exemplary references features for indicating when the prosthesis is and isn’t in the neutral position. Within this context, some background understanding of the biological ankle/foot system may prove helpful.

Figures 3A and 3B give an overview of the behavior of a typical human adult’s natural, fully biological ankle/foot system. To understand prostheses intended to substitute for the human ankle/foot system, it is helpful to briefly summarize the conventional understanding of the human gait cycle. Figure 3A is a general representation of the gait cycle. Figure 3B is a corresponding graph of typical ankle moments during the gait cycle. In the figure lowercase “n” refers to the neutral position of the ankle. The standing position may sometimes be regarded as the neutral position. Ankle angles may also referred to as positions in this disclosure. Ankle angles which are plantarflexed positions arc identified with a lower case “p”. Ankle angles which are dorsiflexed positions are identified with a lowercase “d”. Accordingly, as a few examples, “8p” is a shorthand for 8 degrees of plantarflexion. By contrast, “lOd” is a shorthand for 10 degrees of dorsiflexion. The specific angle measures provided in Figure 3A are fairly representative of desired ankle angles for what may be regarded a healthy adult gait cycle. However, all individuals differ to some degree from one another, and it should be understood that the angles indicated in Figure 3A are selected in particular merely for illustrative purposes.

The human gait cycle is separated into two primary phases described with respect to a single foot: (1) stance phase when the foot is in contact with the ground, and (2) swing phase when the foot is in the air. Generally, when the left foot is in stance phase, the right foot is in the swing phase. Likewise, when the left foot is in the swing phase, the right foot is in the stance phase. There arc five sub-phases to stance phase and three sub-phases to swing phase. The subphases belong to stance phase are shaded in Figure 3A. Though the knee and hip joints are also implicated in the gait cycle, the following brief discussion of gait cycle will focus on the motion at the foot-ankle complex during the gait cycle.

The first sub-phase of stance phase is initial contact (abbreviated in Figure 3A as “IN. CT”). Initial contact occurs when the heel first contacts the ground and is the first 3% of stance phase. It is also referred to as heel strike in some literature; heel strike or initial contact may also be used to describe the moment at which the stance phase begins. Loading response follows initial contact and ends as the foot comes flat to the ground. The foot coming flat to ground typically corresponds with the opposite foot’s toe-off event. During initial contact and loading response, the ankle plantarflexes approximately 8° (to 8p) from the neutral position (n), and the foot comes completely in contact with the ground (also known as foot flat). Neutral position may in some embodiments be interchangeably referred to as standing position. Midstance is next and the ankle articulates from 8° of plantarflexion (8p) to a position of 5° of dorsiflexion (5d). Terminal stance follows and begins as the heel lifts off the ground (“heel off’) and progresses until 10° of dorsiflexion (lOd) is achieved. The final sub-phase of stance phase is pre-swing, during which the foot is preparing to leave the ground. During pre-swing the foot plantarflexes from 10° of dorsiflexion (lOd) to 20° of plantarflexion (20p). Pre-swing concludes with the foot leaving the ground, also known as “toe-off’. The peak ankle moment for stance phase occurs during loading response.

Swing phase is when the foot is in the air. It immediately follows pre-swing and ends with the next initial contact. The first sub-phase of swing phase is initial swing. During initial swing the foot leaves the ground and travels upwards as the knee flexes. The ankle returns from the plantarflexed position (20p) achieved during pre-swing to a roughly neutral position (n). Initial swing ends when the knee stops flexing, which is to say the knee has reached its maximum flexed position. It is typically for the left foot and right foot to be approximately adjacent to one another in the coronal plane, meaning neither foot is appreciably more forward of the other, at the end of initial swing. Mid swing occurs next. It begins as the knee starts to extend and ends when the tibia is approximately vertical to the ground. The ankle slightly dorsiflexes (approximately 2°, from n to 2d) during mid swing to help the toes clear the ground. The final sub-phase of swing phase is terminal swing. During terminal swing the knee extends to nearly full extension, and the foot returns to a neutral position (n) to prepare for the next initial contact.

Figure 3B is a graph depicting the ankle moment of a sound biological ankle/foot as a function of percentage of gait cycle. The ability of a prosthesis to closely replicate or mimic this ankle moment progression depends primarily on two factors: the ankle foot design and the alignment of the prosthesis.

Figure 4 illustrates a perspective view of an example of a prosthetic foot system 100 including a footshell 102 and a prosthetic foot 104. The prosthetic foot 104 is configured to support the user of the prosthetic foot system 100. The footshell 102 is configured to house and protect the prosthetic foot 104 and to have an aesthetic design. The footshell 102 provides an aesthetic covering for the prosthetic foot 104 to give the appearance of an actual foot. The prosthetic foot 104 may be intended to be used inside a shoe in some embodiments. The prosthetic foot system 100 is configured to be mounted to a limb (not shown), such as a residual limb remaining after an amputation. An example of a residual limb may be a residual limb associated with a below-the-knee amputation. In some embodiments, the footshell 102 may be formed as a unitary device without any separate components. In other embodiments, the footshell 102 and the prosthetic foot 104 may be formed as separate components and assembled after the footshell 102 and the prosthetic foot 104 are formed. One or more of the footshell 102 and the prosthetic foot 104, or components thereof, may be formed or manufactured via an additive manufacturing process such as 3D printing, which forms the footshell 102 and/or the prosthetic foot 104 from a three-dimensional lattice network. Some embodiments may omit a footshell 102.

Figures 5A, 5B, 5C, and 5D are various views of the prosthetic foot 104. These figures omit illustration of a footshell 102 for a clearer view of components of the prosthetic foot 104. Figures 5 A, 5B, and 5C are different perspective views, whereas Figure 5D is an exploded view. An exemplary prosthetic foot 104 comprises a spring assembly 116 and an ankle assembly 118.

An exemplary ankle assembly 118 includes a base 186, an extendable link 188, and a prosthetic adapter portion 190 pivotably attached to each other. The extendable link may be, or at least include, a hydraulic cylinder. The ankle assembly 118 may be or include a passive hydraulic damping system that provides the ankle joint member damping rotational resistance, with independent and independently adjustable damping resistances in both the plantarflexion and dorsiflexion directions. Generally, the spring assembly 116 substitutes for a biological foot, and the ankle assembly 118 substitutes for a biological ankle. When in use, these subsystems influence one another such that the behavior and performance of the prosthetic foot 104 derives not from just one or the other subsystem but specifically their combination. That said, the two subsystems may be separable such that the foot spring assembly may be combined with different alternative ankle assemblies, and comparably, the ankle assembly may be combined with different alternative foot assemblies.

The spring assembly 116 includes a base spring 120, a top spring assembly 122, and a heel cushion 124. The spring assembly is rigidly and fixedly attached at a first side 182 of base 186. The top spring assembly 122 is connected to the base spring 120 in a toe end area at a toe end connection 126. The toe end connection 126 may include a bond connection formed by, for example, an adhesive bond. The toe end connection 126 may be formed using an elastic, flexible material that provides at least some relative movement between the base spring 120 and top spring assembly 122 (e.g., rotational movement about a vertical axis, compression, and translational movement in the anterior/posterior and/or medial/lateral direction). The toe end connection 126 may provide the sole connection point between the base spring 120 and top spring assembly 122. Typically, the heel cushion 124 is mounted directly to a top surface of the base spring 120 and arranged to contact a bottom surface of the top spring assembly 122. The heel cushion 124 may be releasably connected to the base spring 120. Alternatively, heel cushion 124 may be releasably connected to the top spring assembly 122. In at least some examples, the heel cushion 124 is connected to the base spring 120 with an interference fit connection using, for example, a retainer 128 that is mounted to the top surface of the base spring 120. The heel cushion 124 may be replaceable with other heel cushions having different properties such as increased or reduced stiffness, compressibility, damping capability, etc. Heel cushions of different sizes and shapes may also be used in place of the heel cushion 124 shown in the figures. In some examples, the prosthetic foot 104 may be operable without any heel cushion 124.

The ankle assembly 118 may be releasably attached to the top spring assembly 122 at its proximal end. In at least one example, the ankle assembly 118 is releasably connected using one or more fasteners 130a, 130b. A prosthetic adapter portion with different connector features such as a pyramid connector 132 may be used, for example, a female pyramid adapter may replace the male pyramid adapter 132. In at least some examples, the pyramid connector 132 is a replaceable component of the ankle assembly 118. In other embodiments, the pyramid connector 132 is integrally formed with remaining portions of the adapter assembly. Other connector features besides a pyramid connector may be used as part of the adapter assembly for securing the prosthetic foot 104 to another prosthetic member such as a lower leg pylon, a socket, or the like.

The base spring 120 is shown including a toe end 134, a heel end 136, a sandal slot 138, and a balance slot 140. The base spring 120 may also include a top surface 142, a bottom surface 144, and the heel cushion retainer 128 positioned at a heel end portion of the base spring 120. The retainer 128 may include a cavity 146 and a rim 148 to help releasably secure the heel cushion 124 to the base spring 120.

The sandal slot 138 may also have a length Ls. The length of the sandal slot 138 is typically in the range of about 0.5 to about 2 inches. The sandal slot 138 is formed in the toe end portion of the base spring 120 and extends posterior from an interior most edge of the base spring 120. The balance slot 140 is also formed at the toe end portion beginning at the anterior most edge of the base spring 120 and extending posteriorly. In at least some embodiments, the balance slot 140 is aligned with a longitudinal center line of the base spring 120. The balance slot 140 may provide enhanced medial/lateral compliance for the prosthetic foot 104, particularly when walking on uneven surfaces.

As shown in at least Figures 5A-5C, the base spring 120 has a contoured shape along its length. The side profile of the base spring 120 undulates between concave and convex shapes. In some examples, the distal surface of the base spring 120 is preferably convex in an anterior section, transitions to concave in an arch or mid- section, and may transition back to convex at the posterior end. These contours and the location of the contours, particularly relative to the toe end connection 126 and the heel cushion 124, may provide improved rollover smoothness, enhanced energy feedback to the user, stability, and comfort during use of the prosthetic foot. Providing the lever portion extending posterior of the heel cushion 124 may also provide improved smoothness in the rollover and energy feedback during use.

The top spring assembly 122 is shown including first and second spring members 150, 152, a first spacer 154 at the toe end portion of the prosthetic foot, a second spacer 156 positioned at a proximal end of the top spring assembly 122 and a gap G provided between the first and second spring members 150, 152 along their entire length. The first and second spring members 150, 152 may be referred to as leaf springs. The first and second spring members 150, 152 may extend generally in parallel with each other along their entire lengths. The first spacer 154 may be provided as a bond connection between the first and second spring members 150, 152. In at least some examples, the first spacer 154 comprises the same bond material as used for the toe end connection 126 between the top spring assembly 122 and the base spring 120. In at least some embodiments, the first spacer 154 is positioned generally in alignment with the toe end connection 126 so as to be positioned vertically above the toe end connection 126, or at least partially overlapping the toe end connection 126 in a length dimension of the base spring 120. The first spacer 154 may provide a permanent connection between the first and second spring members 150, 152. The material of first spacer 154 may provide at least some relative movement between the first and second spring members 150, 152 (i.e., rotational movement about a vertical axis, translational movement in an anterior, posterior or medial/lateral direction, compression, etc.). The material of first spacer 154 may be elastic so as to return to its original shape upon removal of a force that is used to compress or deform the first spacer 154.

In other examples, the first spacer may comprise a wear resistant, low friction material that is attached to one of the first and second springs. The first spacer is not attached or connected to the other of the first and second springs. This arrangement supports compression forces between the distal ends of the first and second springs and allows the springs to separate during plantar flexion and also slide against each other at the distal ends of the springs. Such an embodiment may also alter performance of the foot during rollover in comparison to having the first spacer as a bond connection. Tensile and shear forces are not transferred through the spacer, hence the deflection and stress conditions in the upper spring assembly are modified. The first spring is in an unloaded condition during plantarflexion at heel strike and, as the foot rolls over and the user’s weight is transferred to the toe, shear displacement between the distal ends of the first and second springs results in increased defection the foot in the toe region, thereby softening the foot during both the heel strike and terminal stance portions of the gait cycle.

The second spacer 156 may comprise a rigid material that is non-compressible and/or non-elastic. The second spacer 156 may be positioned at a proximal most end of the top spring assembly 122. The second spacer 156 may be aligned with the ankle assembly 118, or at least portions thereof. In the illustrated embodiment, the second spacer 156 includes apertures through which the fasteners 130a, 130b extend for connection of the ankle assembly 118 to the top spring assembly 122. The first and second spacers 154, 156 may define the size of the gap G when the prosthetic foot 104 is in a rest state. Typically, the gap G is provided along an entire length of the first and second spring members 150, 152 when the prosthetic foot 104 is in a rest state (i.e., prior to application of a force during use of the prosthetic foot 104). Alternatively, the two upper springs 150, 152 may abut (e.g., directly contact each other) at the connector location. The gap G may vary in size during operation of the prosthetic foot 104. For example, the gap G may reduce in size at the first spacer 154 if the material of the first spacer 154 is compressible during use. In another example, the gap G may reduce or change size at locations between the first and second spacers 154, 156 during use. For example, applying a force from a user during a gait cycle may change the size of gap G at various phases of the gait cycle (e.g., at heel strike, stance phase, and toe off), as the forces are applied and released during use by a wearer, those forces arc absorbed and/or fed back through the base spring 120 and heel cushion 124. In at least some embodiments, the first spring member 150 may come into contact with the second spring member 152 during use of the prosthetic foot (i.e., the gap reduces to zero).

The first spring member 150 is shown having an anterior end 158, a proximal end 160, a horizontal portion 162, a slot 164, and fastener apertures 166a, 166b. The second spring member 152 may include an anterior end 168, a proximal end 170, a sloped portion 172, a slot 174, and fastener apertures 176a, 176b. The slot 174 may be aligned with the slot 164 of the first spring member 150 and the balance slot 140 formed in base spring 120. In at least some examples, the slots 140, 164, 174 may extend in a posterior direction to a common location. The slots 140, 164, 174 may terminate at different locations in the anterior direction. The slots 164, 174 may be aligned with a center line of the base spring 120 and top spring assembly 122 so as to provide balanced medial/lateral pronation and compliance during use of the prosthetic foot.

The top spring assembly 122 is mounted to the base spring 120 as shown in at least Figures 5A-5C. The heel cushion 124 is arranged to contact a bottom or downward facing side or surface of the top spring assembly 122 (e.g., a bottom surface of first spring member 150 as shown in Figure 5C). Although the heel cushion 124 is shown connected to the base spring 120 and not the top spring assembly 122, other embodiments may provide the heel cushion 124 connected to both the base spring 120 and top spring assembly 122, or connected only to the top spring assembly 122 (e.g., the retainer 128 is mounted to the bottom surface of first spring member 150 for releasable attachment of the heel cushion 124). The heel cushion 124 may be releasably mounted to the base spring 120 (or top spring assembly 122). Alternatively, the heel cushion 124 may be permanently connected to the base spring 120. The replaceability of heel cushion 124 may provide customization of the amount of heel stiffness, cushioning, energy dampening, and the like provided by heel cushion 124. Heel cushion 124 may be connected with an interference fit connection. Other embodiments may provide for the heel cushion 124 to be secured with a positive connection such as, for example, a fastener, clip, bracket or the like.

The heel cushion 124 may include a top surface 178 (see Figure 5C), a tapered shape having a variable thickness along its length, a bottom surface 180, a top perimeter rim 182, and a bottom perimeter rim 184. The tapered shape may provide for a smaller thickness at an anterior end as compared to a greater thickness at a posterior end of the heel cushion 124, as shown in Figure 5C. The tapered shape of the heel cushion 124 may match the angle and/or curvature of the first spring member 150. As such, the top surface 178 may have a contoured shape rather than a planar shape. Similarly, the bottom surface 180 may have a shape that matches the contour or curvature of the top surface of the base spring 120, as shown in at least Figure 5C.

The heel cushion 124 may comprise a shock absorbing, dampening material such as, for example, silicone or urethane elastomers including, for example, silicone or urethane foams. In some embodiments, the heel cushion 124 may include a plurality of different materials, layers of materials, or separate components that are secured together as an assembly to provide the desired cushioning properties. In one example, the heel cushion 124 includes a foam material encapsulated within a protective polymer shell. In another example, the heel cushion 124 includes a gel material or capsule that is encapsulated within a foam material.

The base spring 120 and first and second spring members 150, 152 may comprise a fiber reinforced composite material such as, for example, carbon fiber reinforced composite. The first spacer 154 may include an adhesive bond comprising a flexible adhesive such as, for example, a urethane adhesive having a Shore A hardness in the range of about 70 to about 95. During manufacture of the top spring assembly 122, the first and second spring members 150, 152 may be bonded together using a removable gasket between the springs to create a sealed space for the adhesive, and the adhesive is then injected into the space.

The second spring member 152 may be shorter in length than the length for the first spring member 150. This difference in length may allow for a somewhat gradual change in stiffness in the top spring assembly 122. Although two spring members 150, 152 are shown as part of the top spring assembly 122, other embodiments may utilize more than two leaf spring elements, and the leaf spring elements may have the same or different lengths.

The second spacer 156 may comprise a lightweight material such as, for example, aluminum, nylon or fiberglass sheet material (e.g., fiberglass G-10). The top spring assembly 122 may provide a connection between the first and second spring members 150, 152 at opposite ends with a gap G provided there between, thereby providing a number of unexpected structural advantages. These advantages in connection with the type of spacers 154, 156, the toe end connection 126, the heel cushion 124, and/or other features may provide a number of performance advantages as compared to known prosthetic feet. For example, a dual, narrow cantilever beam, one located above the other and with a space in between the upper and lower beams, and with frictionless spacer at the free end to transmit an applied vertical force from the upper beam to the lower beam at the free end, may result in about 15-25% reduction in bending stress and about 30-45% reduction in shear stress as compared to an equivalent stiffness single cantilever beam. If the first spacer is comprised of a low friction material connected to one of the first and second springs, the boundary conditions described are highly accurate.

If the first spacer is a bond connection (e.g., created with a flexible material), the boundary conditions are approximately midway between a frictionless spacer between the distal ends of the first and second spring and a rigid connection at the distal ends of the first and second springs. Because stresses are reduced by using the dual upper spring design, a prosthetic foot utilizing this dual spring design exhibits at least one of improved durability and improved flexibility as compared to single spring designs and dual spring designs which are rigidly connected at the distal end. Furthermore, utilizing a low friction spacer material may provide more flexibility than utilizing a flexible bond connection, thus potentially providing opportunities to achieve different and desirable performance characteristics and multiple design options to achieve the designer’s goal. Many of the advantages of the dual cantilever beam designs disclosed herein may be maximized when the two beams (e.g., first and second spring members 150, 152) have substantially equal bending stiffness. If the beams are constructed of unidirectional fiber reinforced composite lamina, the maximum strength/stiffness ratio may be best achieved when both beams have substantially the same lamina orientation and thickness. As the difference between the bending stiffness of the upper and lower beams increases, the advantages of a dual cantilever spring design typically diminish.

The heel cushion 124 may comprise a silicone or urethane elastomer (e.g., an elastomer with the Shore hardness range of about 50A to about 90A). The heel cushion 124 may be retained with retainer 128 in a way that extends around an entire perimeter of the heel cushion 124. Other embodiments may provide for a retainer that extends around only a portion of perimeter of the heel cushion 124. The retainer 128 may be bonded to the top surface 142 of the base spring 120 using, for example, an adhesive. In some embodiments, both the adhesive and the retainer 128 are somewhat flexible to avoid detachment of the retainer 128 from the base spring 120 when the base spring 120 flexes during use. The retainer 128 and adhesive may comprise a plastic material having a Shore hardness in the range of, for example, about 90A to about 50D. Alternatively, the retainer 128 may be cast into the structure of base spring 120 along the top surface 142 thereof, which may eliminate the need for use of an adhesive or other bonding agent.

The retainer 128 may help keep the heel cushion 124 in place by utilizing geometric interlocking features. These interlocking features may include angled (e.g., wedge-shaped) features in the retainer and along an exterior of the heel cushion 124, wherein corresponding surfaces interface to provide a connection The heel cushion 124 may be deformed or compressed in order to fit into the interior of the retainer 128, and then expanded automatically to its original shape thereby creating an interference fit connection between the features of the retainer 128 and the heel cushion 124. Alternatively, the retainer 128 and the heel cushion utilize a rib that fits into a recess, wherein the rib and recess may be formed on either the retainer 128 or heel cushion 124.

Generally, the base spring 120 extends from the toe region to a heel region of the prosthetic foot. The base spring 120 may extend from an interior most point of the prosthetic foot 104 to a posterior most point of the prosthetic foot 104. The top spring assembly 122 may be connected to the base spring 120 at a location spaced posterior of an anterior most edge of the base spring 120. In at least one example, the top spring assembly 122 is positioned posterior of the sandal slot 138 formed at the distal end of the base spring 120. The base spring 120 may extend in an anterior direction at least as far as an anterior most point along a length of the top spring assembly 122. As discussed above, the slot or split 140 formed in the base spring 120 from the anterior edge in a posterior direction may be aligned with the slots or slits 164, 174 formed in the top spring assembly 122 from the anterior end of the top spring assembly 122 extending in a posterior direction. These slots or splits may provide for the entire prosthetic foot 104 to be divided into medial and lateral sides at least in the toe and midfoot regions of the prosthetic foot.

The top spring assembly 122 includes first and second spring members 150, 152 that extend to different anterior positions along the length of the prosthetic foot. At least Figure 5C illustrates the first spring member 150 extending further in an anterior direction than the second spring member 152. The first spacer 154 is positioned at the anterior most edge of the second spring member and spaced posterior of the anterior most edge of the first spring member 150.

The top spring assembly 122 extends generally parallel with the base spring 120 in the toe, midfoot, and heel regions of the base spring 120. As described above, other embodiments may provide for the top spring assembly 122 to continue extending in a generally horizontal or slightly angled direction relative to the base spring 120 and/or a horizontal plane through the heel end portion.

Additionally, the gap G may be substantially constant when the prosthetic foot 104 is in a rest or unloaded state. During use of the prosthetic foot 104, portions of the first and second spring members 150, 152 may move toward and/or away from each other to alter the size of gap G at various locations along the length of the top spring assembly 122. In at least some embodiments, portions of the first and second spring members 150, 152 may contact each other.

The fasteners 130a-b may be arranged side-by-side in a medial/lateral direction. In other arrangements, the fasteners 130a-b may be arranged in alignment with a length dimension of the prosthetic foot 104. Although only two fastener 130a-b are shown in Figure 5C, only one or more than two fasteners 130a-b may be used. The fasteners 130a-b may provide a positive connection between the first and second spring members 150, 152, a positive connection between the top spring assembly 122 and the ankle assembly 118, and/or a positive connection between one or both of the first and second spring members 150, 152, and the spacer 156. In some examples, the fasteners 130a-b are connected directly to one or both of the first and second spring members 150, 152 (e.g., to a threaded seat formed in one or both of the first and second spring members 150, 152), or may be connected to a nut (not shown) positioned on an opposite side of the top spring assembly 122. The prosthetic foot 104 may provide energy feedback, stability, force dampening and the like associated with the use of spaced apart spring members in the top spring assembly 122, the use of a heel cushion 124 arranged in the specific location and having the size and shape shown in Figure 5C, the shape and size of the top spring assembly 122 and base spring 120, and the size, shape, and orientation of the ankle assembly 118. Furthermore, the base spring 120 and top spring assembly 122 may include slots (e.g., slot 140 for base spring 120 and slots 164, 174 for first and second spring members 150, 152) that provide medial/lateral pronation and ambulation for the prosthetic foot 104, which may provide improved stability for the user, particularly on uneven ground surfaces.

The prosthetic foot 104 may be a dual or multiple toe spring prosthetic foot. The prosthetic foot 104 may be a single toe spring prosthetic feet. The heel assemblies, adapter assemblies, attachment assemblies, and other features disclosed with reference to any single embodiment disclosed herein may be interchangeable with features of other prosthetic foot embodiments disclosed herein.

In alternative embodiments, the connection between the base spring and the top spring assembly and between the first and second spring members in the anterior region of the foot and may be provided with bolts or other fasteners. A rigid spacer may be provided between the spring members and/or between the top spring assembly and the base spring. The use of bolts or other fasteners in combination with an altered geometry of the first and second spring members may eliminate gaps that may otherwise exist at connection points at the anterior end of the prosthetic foot. In another embodiment, a connection between the first and second spring members may be made by wrapping carbon fiber or glass fiber around the first and second spring members at the connection point between the first and second spring members, and securing the spring members and the fiber by impregnating the fiber with epoxy or similar thermosetting resin. A similar connection may be made between the top spring assembly and the base spring.

In another example, the connection at the proximal end of the top spring assembly may be created by altering a geometry of the first and second spring members such that no gap exists at the connection points between the first and second springs. In this arrangement, a gap may still be provided between the first and second spring members at other locations along their lengths. In some embodiments, one or more of the first and second spring members may be inserted into a slot formed in the prosthetic connector (e.g., base 186 of ankle assembly 118), and the first and second spring members are secured together and to the prosthetic connector with an adhesive or a fastener.

Discussion now turns to the exemplary ankle assembly 118 depicted by Figures 5A-5D. As briefly mentioned above, an exemplary ankle assembly 118 includes a base 186, an extendable link 188, and a prosthetic adapter portion 190 pivotably attached to each other. The ankle assembly 118 provides the user a more natural feel during the gait-cycle. An ankle assembly 118 gives the amputee some fluid-like movement during normal use, not a more rigid feel that is associated with the typical prosthetic foot. Specifically, an exemplary ankle assembly may include one or more (up to all of) the following features: (1) a dorsi flexion stop which limits the dorsiflexion rotation of the ankle assembly, transferring load to the composite spring or springs located in the forefoot area of a foot assembly, allowing the composite springs to provide support and store energy (2) a soft dorsi flexion stop that improves the transition between the hydraulic resistance and spring resistance created by the composite foot spring elements; (3) a manual hydraulic lock which prevent plantarflexion of the ankle such that when the ankle reaches maximum dorsiflexion it will be locked; (4) a volume compensator that maintains the hydraulic system at a preloaded pressure on the fluid and compensates fluid loss; (5) a hydraulic lock that may lock the ankle in any position to enable the user to use different height heels (shoes) with the same prosthetic ankle and foot; (6) an improved hydraulic geometry; and (7) one or more springs configured to store energy during plantarflexion rotation of the ankle assembly and release stored energy during dorsiflexion rotation of the ankle assembly. In some embodiments some of these features may be omitted.

The improved hydraulic geometry may entail locating the ankle pivot points such that a high percentage of the axial load is supported by the pivot structure when the user is standing. Furthermore, the hydraulic cylinder has improved leverage about the base and foot spring pivot point, reducing the pressure of the hydraulic fluid in the system and reducing the required strength and mass of the hydraulic cylinder. Resulting advantages further include increased cycle life and seal integrity.

An exemplary ankle assembly 118 enables both plan tarflexion motion and dorsiflexion motion of the prosthetic foot 104. Enabling plantarflexion motion at an ankle joint allows the metatarsophalangeal (ball of foot) area of the foot to achieve contact with the ground earlier in the gait cycle. The ball of foot/wide part of the foot provides stability during the gait cycle. The ankle assembly 118 also enables a small amount of dorsiflexion, relative to a standing position, which results in reduced and adjustable resistance to tibial progression when the prosthetic shin is vertical or near vertical when compared to a prosthetic foot without an ankle assembly. When an amputees’ center of mass is directly above the shin and the shin is vertical, the amputee does not have much leverage over the lever arm created by the forefoot of a prosthetic foot. The ankle assembly 118 mitigates this limitation of prosthetic feet.

As described below, the rotation axis of the foot spring assembly is forward of the pyramid axis of the pyramid connector 132. Therefore, the center of mass (COM) of the amputee is directly above the rotation axis when standing, allowing amputees to stand without significant movement of the ankle assembly 118. This design feature also minimizes impact when the ankle reaches the end of its hydraulic range in the dorsiflexion direction (the dorsiflexion stop).

An ankle assembly 118 may comprise both a dorsiflexion stop and a plantarflexion stop. A dorsiflexion stop is a component, or assembly of components, which establishes a maximum dorsiflexion angle for the ankle assembly 118 and prosthetic foot 104. A plantarflexion stop is a component, or assembly of components, which establishes a maximum plantarflexion angle for the ankle assembly 118 and prosthetic foot 104. An exemplary dorsiflexion stop may comprise, for example, a dorsiflexion stop bumper that reduces or eliminates an impact at the end of the dorsiflexion travel. As the ankle assembly 118 dorsiflexes, it eventually reaches the end of its hydraulic range-of-motion. At this point the flex of the spring assembly 116 takes over and starts to bend. If this transition were abrupt, it would not be comfortable for the amputee. The dorsiflexion stop bumper gradually squeezes as the ankle assembly 118 reaches this transition point, allowing a smooth transition from the hydraulic function to the flexing function of the spring assembly 116. Additionally, the dorsiflexion stop bumper may be low-profile disc springs that would respond is a similar way as the elastomeric stop and provide a smooth transition between the hydraulic function and the composite spring function of the ankle assembly 118 and spring assembly 116. A dorsiflexion stop in any embodiment may alternatively not include any bumper at all. The dorsiflexion stop may be engaged at, for example, a 0°, 2°, or 4° ankle position, or the standing position. This assists an amputee with standing up straight.

A plantarflexion stop may, for example, be established simply by the displacement distance of the hydraulic cylinder’s piston within the piston cavity. When the hydraulic piston reaches a maximum travel position in the cylinder, no further travel of the piston and shaft is possible. Once the piston reaches a maximum travel position (whether in the dorsi flexion or plantar flexion positions corresponding to maximum or minimum cylinder extension) it is still free to move away from this maximum position and return to another position within the range of piston travel.

The base 186 has a first/bottom side 192 and a second/top side 194. The first side 192 is sized and shaped to correspond to a shape of the first spring member 150 such that the posterior end of the first side 192 is arranged substantially flush with the first spring member 150. The second side 194 is sized and shaped to accommodate three sets of bore holes that attach the base 186 to the first spring member 150, the hydraulic cylinder of the extendable link 188, and the prosthetic adapter 190. Specifically, the base 186 defines a first set of bore holes 196a, 196b, a second set of bore holes 198a, 198b, and a third set of bore holes 200a, 200b. The first set of bore holes 196a, 196b are configured to receive fasteners 130a, 130b that fasten the base 186 to the first spring member 150. The second set of bore holes 198a, 198b are configured to receive a portion of the extendable link 188 to maintain a position of the extendable link 188 while allowing the extendable link 188 to rotating relative to the base 186. Similarly, the third set of bore holes 200a, 200b are configured to receive a portion of the prosthetic adapter 190 to maintain a position of the prosthetic adapter 190 while allowing the prosthetic adapter 190 to rotating relative to the base 186. The base 186 is a monolithic and rigid part which does not function as a spring and exhibits no appreciable deflection or deformation during use and is made of a lightweight metal, for example aluminum, magnesium or titanium.

The prosthetic adapter 190 defines a bore 202 configured to receive the pyramid connector 132, a cavity 204 configured to receive a portion of the extendable link 188, a fourth set of bore holes 206 configured to receive a piston fastener 208, and a base bore 210 configured to receive a base fastener 212. The prosthetic adapter 190 is sized and shaped to accommodate the pyramid connector 132, the cavity 204, the fourth set of bore holes 206, the piston fastener 208, the base bore 210, and the base fastener 212. Specifically, the prosthetic adapter 190 includes a first portion or bulbous portion 214 and a second portion or tapered portion 216. The bulbous portion 214 defines the cavity 204 and is bulbous to enable the cavity 204 to be voluminous enough to receive a portion of the extendable link 188. Additionally, the bulbous portion 214 is large enough to define the bore 202 and the fourth set of bore holes 206 to accommodate the pyramid connector 132 and the piston fastener 208. The tapered portion 216 is smaller than the bulbous portion 214 such that the taper portion 216 is received between the third set of bore holes 200a, 200b of the base 186. The base fastener 212 extends between the third set of bore holes 200a, 200b and through the base bore 210 to attach the prosthetic adapter 190 to the base 186.

Figures 6, 7, and 8 illustrate exemplary reference features applied to the prosthetic foot 104 introduced above. The prosthetic foot comprises a three-dimensional edge 501 which pairs with an indicium 502 as first and second reference features, respectively. These features 501 and 502 have a spatial relation with one another that changes based on the rotational position of the joint generally, and the rotational position of the prosthetic adapter 190 relative the extendable link 188 specifically. The spatial relation of features 501 and 502 particularly indicates when the links of the prosthetic joint are arranged in the neutral rotational position (and correspondingly the joint as a whole is in its neutral position), and likewise when they are not.

The combination of features 501 and 502 together conveys whether the prosthetic joint is in the neutral position. When the features 501 and 502 appear aligned, the prosthetic joint is in the neutral position. Said differently, alignment of the features 501 and 502 conveys, by visual inspection alone, that the prosthetic joint is in the neutral position. Whenever the features 501 and 502 do not appear aligned, which is to say they appear separated by a distance from one another, the prosthetic joint is not in the neutral position. Said differently, non-alignment of the features 501 and 502 conveys, by visual inspection alone, that the prosthetic joint is not in the neutral position.

Alignment of two reference features like features 501 and 502, especially the perception of alignment by the general visual inspection of a prosthetist, as used in this disclosure inherently permits a certain margin of acceptable deviation from what may be called “perfect” or “absolute” alignment. As a non-limiting but exemplary example, the first reference feature 501 and second reference 502 are sized, shaped, and arranged on exteriors of the separate moving parts of the joint such that one degree or more of rotation out of the neutral rotational position corresponds with the first reference feature 501 and second reference feature 502 being at least 0.5 mm distant relative to one another, or 1 mm distant from one another. The threshold is significant because it takes into account the natural abilities of the unaided human eye. From a distance of a few feet, the unaided human eye can fairly reliability perceive that two things are in fact separated by a perceptible distance if the distance is at least 0.5 mm, or at least 1.0 mm, for example. At smaller separation distances, the ability to readily discern a separation between two things becomes more difficult for an ordinary observer situated a distance of a few feet away. Accordingly, a 0.5 or 1 mm threshold serves as a reliable basis for a prosthetist holding the joint up to arm’s distance away from his or her face and reliable recognizing whether the two features 501 and 502 appear to be aligned or not aligned. The up to one degree of rotation permitted to occur while the two features may still appear aligned (e.g., with a separation distance of less than 0.5 mm) constitutes an exemplary margin of error from what may be called “true” or “absolute” neutral position. Alternative embodiments may vary the 0.5 mm threshold, or 1 degree accepted of margin of error, based on other considerations, e.g., how close prosthetists are willing to hold devices to their eyes and the particular size, shape, and arrangement of the reference features for a given embodiment.

As features 501 and 502 of Figures 6-8 demonstrate, one or both of the exemplary references features may be any (or a combination of) the following: a two-dimensional indicium, a three-dimensional indicium, an engraving, a line, a curve, an edge, a border, or a boundary. These examples are non-limiting and, as their ordinary meanings convey, overlap in various respects. For example, a physical three-dimensional edge of a shaped solid (e.g., metal or plastic of the prosthetic) may be accurately described also by the more general term, 3D indicium. Of course, not all visually apparent lines, curves, edges, and the like of the prosthetic joint qualify as indicia. Indicia, as used in this disclosure, describes only those features which have particular and deliberate significance in relation to at least one other feature. The particular and deliberate significance is that the spatial relation between the at least two features changes based on the rotational position, and the spatial relation visually communicates in a reliable and reproducible manner whether or not the prosthetic joint is in a rotational position of particular significance, e.g., the neutral position.

At least one reference feature from every pair of reference features exists (or is configured with a particular visual appearance) for no purpose other than the visual communication of whether or not the prosthetic joint is in the neutral position. The second reference feature of the pair may likewise exist for no purpose other than this purpose as well. Alternatively, the second reference feature may have some other purpose or utility, e.g., it may be a three-dimensional feature such as an edge of one of the links and pail of the housing of such link. In Figure 6A the ankle assembly is exploded so the adapter portion 190 is displaced to provide a clearer view of the extendable link 188. Features 504, 502, and 503 arc visible. Feature 504 indicates the angular orientation when the extendable link is at maximum length. Feature 502 represents a neutral position. Feature 503 indicates the angular orientation at the minimum length of the extendable link. If an embodiment has one neutral position, this position may be indicated with a single mark. However, providing marks which indicate the maximum and minimum limits of angular orientation may be desired in some embodiments, giving the user a feel for the sensitivity of the angular orientation and indicating where the neutral position is located within the range of possible angular orientations.

Figure 6B shows the angle assembly from a perspective view which provides a clear view of the physical edge of adapter portion 190 serving in this exemplary embodiment as feature 501. Alignment features appear on the left side of the ankle assembly. Embodiments may include alignment features in any of a variety of positions on a joint assembly, including, for example but not limited to, on a right hand side (see Fig. 6A for instance), on a left hand side (see Figure 6B for instance), or on multiple sides such as both right and left sides. In Figure 6B the assembly is positioned at a maximum dorsiflexion position. Accordingly feature 504 is aligned with feature 501. Features 502 and 503 are visible and clearly not aligned with feature 501, each being spaced a visibly apparent distance apart from feature 501.

In Figure 7A, the features 501 and 502 are visibly spaced apart, and therefore a prosthetist may conclude the prosthesis is not in the neutral position. In fact, Figure 7A depicts the prosthesis at the max dorsiflexion position. Features 501 and 504 are aligned. In Figure 7B, the features 501 and 502 coincide spatially. Feature 501 appeal's directly at or atop feature 502. The alignment of the features 501 and 502 conveys, based on visual observance alone, that the prosthesis is in the neutral position in Figure 7B. In Figure 7C, the feature 502 is no longer even visible, owing to the feature 501 having moved past the feature 502 and the body of the prosthetic adapter 190 obscuring feature 501 from view.

Exemplary embodiments may include reference features for purposes of indicating positions other than the neutral position. For example, in Figure 7A the prosthesis includes a reference feature 503 which is a max plantarflexion line. When feature 501 aligns with feature 503, the prosthesis is maximally plantarflexed. The alignment of features 501 and 503 conveys visually that the prosthesis is at the maximum plantarflexion position. In a joint with three or more links, reference features may be provided for characterizing the relative positions of any pair of connected links within the assembly. Taking the ankle assembly 118 as an example, each of the three links in the force triangle are directly connected with the other two links. Reference features conveying a particular position of the assembly, such as the neutral position, may be provided on just links 188 and 190 (e.g., as illustrated), or else on just links 188 and 186, or else on just links 186 and 190. Alternatively, reference features may be provided on any two of such link pairings. As yet a further alternative, reference features may be provided on all three link pairings. Alignment of reference features for one link pairing may or may not signify something different from alignment of reference features for a separate link pairing. For instance, a first set of reference features (for a first link pairing) may signify a neutral position when aligned, whereas a second set of reference features (for a second link pairing) may signify a maximum flexion position when aligned. Alternatively, the second set of reference features may signify neutral position when aligned, thereby making the second set of reference features deliberately redundant in function to the first set of reference features. Such a redundancy may still have its own utility, e.g., by offering alternative places on the prosthetic a prosthetist may inspect for checking the angular position of the prosthetic.

Figure 8A depicts an ankle assembly of base 186, extendable link 188, and prosthetic adapter portion 190 together with a temporarily attached alignment link 504. The alignment link 504 is temporarily connectable to the ankle assembly. Connectors such as pins 505 and 506 provide for the temporary connection of the alignment link 504 to the prosthetic adapter portion 190 and base 186, respectively. The alignment link 504 is configured to constrain the ankle assembly such that the base 186, extendable link 188, and prosthetic adapter portion 190 are forced into fixed angles with respect to one another. The ankle assembly is forced to assume and maintain a single position within its usual range of pivoting motion. So long as the alignment link 504 remains attached by pins 505 and 506, the angular positions of the base 186, extendable link 188, and prosthetic adapter portion 190 are fixed relative to one another. The length of the alignment link 504 is chosen such that when the alignment link 504 is connected to the ankle assembly, the ankle assembly is fixed in a particular target position, e.g., the neutral position. Once desired alignment of the prosthesis is finished, the alignment link 504 is removed so that the base 186, extendable link 188, and prosthetic adapter portion 190 are again able to move within their intended ranges of motion relative to one another. The alignment link 504 is specifically used for alignment procedures only. The alignment link 504 is not employed during the amputee’s use of the prosthesis.

Figure 8B depicts an ankle assembly of base 186, extendable link 188, and prosthetic adapter portion 190 together with an alignment link 509. Alignment link 509 functions like alignment link 504 of Figure 8A. However, alignment link 509 does not connect to the ankle assembly with connectors like pins. Instead, use of the alignment link requires closing the angle between the base 186 and adapter portion 190 until firm abutment is achieved between end 507 of the alignment link 509 and the adapter portion 190 and firm abutment is achieved between end 508 of the alignment link 509 and the base 186. With the ends 507 and 508 of the alignment link so seated within the ankle assembly, it is impossible to reduce the angle formed by prosthetic portion 190 and base 186 further. This minimum angle corresponds with the target position, e.g., neutral position.

An exemplary method for alignment of a prosthesis or orthotic that comprises a joint assembly with a range of pivoting motion may include the following steps: temporarily attaching or positioning an alignment link with a fixed length within the joint assembly such that the joint assembly is fixed at a single target position within the range of motion; performing one or more alignment procedures to the prosthesis or orthotic while the alignment link is in the joint assembly; and removing the alignment link to permit the joint assembly to move through the range of pivoting motion. Compression of the rotating pails may be initially necessary to set and also maintain the target position. Or at least no extension force should be present once the target position is set.

A position indicated by a reference feature or obtained by an attached alignment link may place a joint in any target position. For purposes of exemplary illustration, marking 502 provides a visual indication of where the neutral position is relative to the range of travel and alignment link 504 likewise fixed the ankle assembly into the neutral position so long as it remained attached to the adapter 190 and base 186. In some embodiments, however, a marking like marking 502 may indicate a target position which is not associated with a neutral position. In some embodiments, an alignment link 504 may be set to or settable to a length which, once attached to the joint assembly, fixes the joint in a target position which is not associated with a neutral position. In some embodiments there may be multiple reference features indicating multiple target positions indicated by multiple reference features, the multiple reference features all located within the travel limits of the joint.

Figure 9 depicts a non-limiting example of an exemplary prosthetic leg 900 which comprises a socket 901 (e.g., configured to receive and conform to an amputee’s amputated limb), prosthetic adapters 902, a pylon 903, and prosthetic foot system 100. The ability to set a prosthesis reliably and reproducibly at a particular angle (such as but not limited to neutral position) enabled by exemplary embodiments of this disclosure is particularly helpful to persons such as prosthetists who are tasked with performing alignments of a prosthesis to suit the product to a particular user. It is desirable during bench alignment and/or dynamic alignment, which are discussed in the Background section above, to be able to place a prosthesis efficiently and accurately in the neutral position, for example. Indeed, exemplary methods may comprise a step of performing one or more alignment procedures (e.g., steps of bench alignment and/or dynamic alignment) to the prosthesis while, e.g., the first and second reference features discussed in embodiments above are aligned with one another, or else when an alignment link such as that depicted by either Figure 8 or 9 is in place. Those of ordinary skill in the art will appreciate that reference in this disclosure to performing an alignment procedure for/of a prosthetic joint may be regarded as implicitly entailing alignment of any of one or more parts of the whole prosthesis of which the prosthetic joint is one aspect. For instance, taking the prosthetic leg 900 of Figure 9 as a non-limiting example of a whole prosthesis, an alignment procedure referring to alignment of a foot system 100 or ankle joint thereof may entail making adjustments to just the ankle assembly within the foot system, or to the ankle assembly and the foot spring assembly, or to one or more of the ankle assembly, the foot spring assembly, prosthetic adapter(s) 902, and/or other components. It will be appreciated that different prostheses may entail adjustments to different components than those just listed during, e.g., bench alignment and/or dynamic alignment, depending on the natural joint or joints and related body parts for which the prothesis is intended to substitute.

Figure 10 illustrates the prosthetic foot system 100 positioned on a flat, horizontal ground surface 372 in a neutral stance such that a pyramid angle 374 between the top surface of the pyramid connector 132 is 0°. As shown in Figure 10, the pyramid connector 132 defines a pyramid connector axis 376 through a middle of the pyramid connector 132 which is oriented vertically. The piston assembly 220 defines a piston axis 378 through a middle of the shaft 222. Figure 11 illustrates the prosthetic foot system 100 positioned on the flat surface 372 at maximum plantarflcxion such that the pyramid angle 374 of the pyramid connector 132 is 0°. In the embodiment illustrated in Figure 11, the first pivot distance 386 is about 50 millimeters (mm) to about 60 mm or about 58.8 mm, the second pivot distance 388 is about 25 mm to about 40 mm or about 33.0 mm, the third pivot distance 390 is about 50 mm to about 60 mm or about 52.5 mm, the moment arm 392 is about 25 mm to about 40 mm or about 32.8 mm, the pyramid axis distance 394 is about 19 mm to about 26 mm or about 23.0 mm, the axis angle 396 is about 15° to about 20° or about 18.3°, the top spring angle is about 20° to about 30° or about 29.1°, and the heel distance 400 is about 30 mm to about 40 mm or about 30.23 mm.

Figure 12 illustrates the prosthetic foot system 100 positioned on the flat surface 372 when the prosthetic foot system 100 is arranged in a shoe (not shown) such that the pyramid angle 374 of the pyramid connector 132 is 2°. The heel distance 400 is a typical shoe heel height of about 5 mm to about 20 mm or about 10 mm. The shoe heel height is the difference in thickness of a shoe sole between a metatarsal region and a heel region. In the embodiment illustrated in Figure 12, the first pivot distance 386 is about 50 millimeters (mm) to about 60 mm or about 58.8 mm, the second pivot distance 388 is about 25 mm to about 40 mm or about 33.0 mm, the third pivot distance 390 is about 50 mm to about 60 mm or about 57.5 mm, the moment arm 392 is about 25 mm to about 40 mm or about 32.0 mm, the pyramid axis distance 394 is about 19 mm to about 26 mm or about 23.0 mm, the axis angle 396 is about 15° to about 20° or about 17.4°, and the top spring angle is about 20° to about 30° or about 22.3°.

Figure 13 illustrates the prosthetic foot system 100 positioned on the flat surface 372 at maximum dorsiflexion such that the pyramid angle 374 of the pyramid connector 132 is 0°. In the embodiment illustrated in Figure 13, the first pivot distance 386 is about 50 millimeters (mm) to about 60 mm or about 58.8 mm, the second pivot distance 388 is about 25 mm to about 40 mm or about 33.0 mm, the third pivot distance 390 is about 50 mm to about 60 mm or about 58.6 mm, the moment arm 392 is about 25 mm to about 40 mm or about 31.7 mm, the pyramid axis distance 394 is about 19 mm to about 26 mm or about 23.0 mm, the axis angle 396 is about 15° to about 20° or about 17.1°, and the top spring angle is about 10° to about 20° or about 18.2°. Both the heel and forefoot area are on the ground.

The foregoing description, for purpose of explanation, has been described with reference to specific embodiments. However, the illustrative discussions above are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations arc possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the present systems and methods and their practical applications, to thereby enable others skilled in the art to best utilize the present systems and methods and various embodiments with various modifications as may be suited to the particular use contemplated.

Where a range of values is provided in this disclosure, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges and are also encompassed within the invention, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the invention.

Unless otherwise noted, the terms “a” or “an,” as used in the specification and claims, are to be construed as meaning “at least one of.” In addition, this statement is intended to serve as antecedent basis for use of such exclusive terminology as “solely”, “only”, and the like in connection with the recitation of claim elements, or use of a “negative” limitation. In addition, for ease of use, the words “including” and “having,” as used in the specification and claims, are interchangeable with and have the same meaning as the word “comprising.” In addition, the term “based on” as used in the specification and the claims is to be construed as meaning “based at least upon.”

As will be apparent to those of skill in the art upon reading this disclosure, each of the individual embodiments described and illustrated herein has discrete components and features which may be separated from or combined with the features of any of the other several embodiments without departing from the scope or spirit of the present invention. Any recited method can be carried out in the order of events recited or in any other order which is logically possible.

While exemplary embodiments of the present invention have been disclosed herein, one skilled in the ail will recognize that various changes and modifications may be made without departing from the scope of the invention as defined by the following claims.

Claims

CLAIMS What is claimed is:

1. A prosthetic joint for external use, comprising a joint assembly comprising a first link comprising a first reference feature, a second link rotatably attached to the first link to define a first pivot point, wherein the second link comprises a second reference feature, and a third link rotatably attached to the first link to define a second pivot point and rotatably attached to the second link to define a third pivot point; wherein the prosthetic joint is rotatable through a range of angles from a maximum flexion position to a maximum extension position, wherein the first reference feature and the second reference feature have a spatial relation that changes based on an angle of rotation of the prosthetic joint, and wherein an alignment of the first and second reference features indicates the joint assembly is in a neutral position, and a non-alignment of the first and second reference features indicates the joint assembly is not in the neutral position.

2. The prosthetic joint of claim 1, wherein the first and second reference features are each an indicium or three-dimensional edge or contour.

3. The prosthetic joint of claim 2, wherein the prosthetic joint is a prosthetic ankle.

4. The prosthetic joint of claim 1, wherein the first and second reference features are both simultaneously visible on an exterior of the prosthetic joint for at least some angles within the range of angles.

5. The prosthetic joint of claim 1, wherein the first and second reference features are configured such that a physical distance between the first and second reference features visibly increases in size when the prosthetic joint is rotating (i) away from the neutral position and (ii) toward the maximum flexion position and/or maximum extension position, and/or the physical distance between the first and second reference features visibly decreases in size when the prosthetic joint is rotating (i) toward the neutral position and (ii) away from the maximum flexion position and/or maximum extension position.

6. The prosthetic joint of claim 1, wherein the first and second reference features are sized, shaped, and arranged on exteriors of the first and second links, respectively, such that one degree or more of rotation out of the neutral rotational position corresponds with the first reference feature being at least 0.5 mm distant from the second reference feature.

7. The prosthetic joint of claim 1, wherein the prosthetic joint is a prosthetic ankle.

8. A prosthetic joint for external use, comprising a joint assembly comprising a first link rotatably connected to a second link such that an angle between the first link and the second link is changeable between a minimum angle and a maximum angle, wherein the joint assembly is configured to have a neutral position corresponding to a single angle measure between the minimum angle and the maximum angle, wherein the first link comprises a first reference feature and the second link comprises a second reference feature, wherein the first reference feature and the second reference feature have a spatial relation that changes based on the angle between the first and second links, wherein an alignment of the first and second reference features indicates the joint is in the neutral position, and a non-alignment of the first and second reference features indicates the joint is not in the neutral position.

9. The prosthetic joint of claim 8, wherein the minimum angle corresponds with a limit to flexion of the joint assembly and the maximum angle corresponds with a limit to extension of the joint assembly.

10. The prosthetic joint of claim 8, further comprising a third link rotatably connected to the first link and to the second link to define a force triangle among the first, second, and third links, wherein at least one of the first link, second link, and third link is extendable to any of a plurality of different lengths.

11. The prosthetic join of claim 10, wherein the joint is an ankle joint.

12. The prosthetic joint of claim 8, wherein the first and second reference features are each an indicium or three-dimensional edge or contour.

13. The prosthetic joint of claim 8, wherein the first and second reference features are both simultaneously visible on an exterior of the prosthetic joint for at least some angles between the minimum and maximum angles.

14. The prosthetic joint of claim 8, wherein the first and second reference features are configured such that a physical distance between the first and second reference features visibly increases in size when the joint is changing position (i) away from the neutral position and (ii) toward the maximum angle and/or minimum angle, and/or the physical distance between the first and second reference features visibly decreases in size when the joint is changing position (i) toward the neutral position and (ii) away from the maximum angle and/or minimum angle.

15. The prosthetic joint of claim 8, wherein the first and second reference features are sized, shaped, and arranged on exteriors of the first and second parts, respectively, such that one degree or more of rotation out of the neutral rotational position corresponds with the first reference feature being at least 0.5 mm distant from the second reference feature.

16. The prosthetic joint of claim 8, wherein the joint is an ankle joint.

17. A method for alignment of a prosthesis for external use that comprises a joint assembly with a range of pivoting motion, the joint assembly comprising a first link rotatably connected to a second link such that an angle between the first link and the second link is changeable between a minimum angle and a maximum angle, wherein the joint assembly is configured to have a neutral position corresponding to a single angle measure between the minimum angle and the maximum angle, the method comprising placing the joint assembly in the neutral position by aligning a first reference feature on the first link with a second reference feature on the second link, wherein the first reference feature and the second reference feature have a spatial relation that changes based on the angle between the first and second links, wherein an alignment of the first and second reference features indicates the joint assembly is in the neutral position, and a non-alignment of the first and second reference features indicates the joint assembly is not in the neutral position; and performing one or more alignment procedures to the prosthesis while the first and second reference features are aligned.

18. The method of claim 17, wherein the one or more alignment procedures align a prosthetic ankle.